bug [ 1248199 ] shelve .sync operation not documented
diff --git a/Doc/lib/libshelve.tex b/Doc/lib/libshelve.tex
index 9e9f7fe..8bd204e 100644
--- a/Doc/lib/libshelve.tex
+++ b/Doc/lib/libshelve.tex
@@ -42,6 +42,14 @@
the transition from dictionary based scripts to those requiring persistent
storage.
+One additional method is supported:
+\begin{methoddesc}[Shelf]{sync}{}
+Write back all entries in the cache if the shelf was opened with
+\var{writeback} set to \var{True}. Also empty the cache and synchronize
+the persistent dictionary on disk, if feasible. This is called automatically
+when the shelf is closed with \method{close()}.
+\end{methoddesc}
+
\subsection{Restrictions}
\begin{itemize}